Fruit fly white larvae in raspberries

Asked July 16, 2018, 4:54 PM EDT

I haven’t seen the adult but I’m quite sure I have these numerous pests. What chemical can be used & when? Thanks

Washington County Minnesota

3 Responses

Most likely what you have is spotted wing drosophilia (SWD), a relative of the fruit fly that has become an agricultural pest for soft fruits like raspberries.

Unfortunately once the fruit is infested, there isn't really a chemical control to be used - what you will need to do is manage it with cultural controls which include proper garden sanitation and possibly exclusion (netting is a good option.)

Sanitation is important to reduce the local buildup of SWD populations.

  • Frequently harvest crops to ensure ripe fruits are not in gardens for extended periods of time.
  • Remove and destroy any old fruit that remains on stems or that has fallen to the ground.
  • Once infested or fallen fruit has been collected, place it in a plastic bag and seal it tightly.
  • Fruit in clear bags can be left outdoors where the heat from the sun will kill any flies in the bag.
  • Plastic bags can also be placed in the trash.
  • Do not compost this material as that method is unreliable in killing SWD.
  • Do not bury infested material as research has found that SWD can survive being buried as deep as 18 inches.
Source: https://extension.umn.edu/yard-and-garden-insects/spotted-wing-drosophila-home-gardens

Please address if the larvae will leave the raspberries after about 15 minutes in warm water. Many exit, but do they all?

I can't really answer that with certainty. The larvae are not harmful to humans if eaten though, so it's not a health concern if some remain in the fruit.